Electric motors are commonly used in a variety of applications. Such motors are electric machines that generate torque (or force, in the case of a linear motor) when supplied with an electric current. One type of electric motor is a DC brushless motor. When paired with a position sensor in a feedback loop, a DC brushless motor can provide accurate position control.
Electric motors may be used in a variety of applications. For example, teleoperative surgery involves the use of manipulator arms that move a medical instrument in a variety of spaces. Specifically, a brushless motor may be used to change the rotation, pitch, yaw, or position of a medical instrument. The brushless motor allows the operator of the instrument to put the device in a specific position based on putting the motor corresponding to each type of movement in a specific position.
Generally, there exists a fixed, nominal mapping between the current supplied to the motor, and the torque it produces. In reality, this mapping from the input current to the output torque of a brushless motor is generally not uniform over one rotor revolution. Specifically, at different rotation angles, the motor may produce a different torque output with the same input current. This is often referred to as a torque ripple. Torque ripples can affect the performance of the motor, and thus it is desirable to minimize or eliminate torque ripples.